Aircraft power systems are known to use electromechanical switches, such as contactors, for numerous reasons. It is desirable to maintain substantially uninterrupted power supply to modern aircraft systems during fault conditions and during switching between power supplies, such as when switching between battery, ground power, and/or alternator power. However, electromechanical switches are typically heavy and are generally less reliable than semiconductor switching devices.
As referenced in U.S. Pat. No. 6,091,596, it might be possible to use electronic switching as a partial or complete replacement for electromechanical switches, such as contactors. However, it is acknowledged that such systems have not been developed for typical power supply systems, and electronic switching is furthermore noted as causing problems with heat dissipation in semiconductor switching devices.
FIGS. 4A and 4B illustrate an exemplary prior art power grid, or master control unit, 120 for a small aircraft power system using electromechanical switches in the form of contactors 44-47. Power grid 120 includes an alternator 52, a starter 54, a ground power supply 56, a battery 58, a clock 60, an alternator control unit 62, a charge/discharge meter 64, a starter switch 66, a master switch 68, and a power output connector 70. Contactor 44 is an alternator contactor, contactor 45 is a starter contactor, contactor 46 is a ground power contactor, and contactor 47 is a battery contactor. Hence, four contactors 44-47 are used in this relatively simple power grid 120 which amplifies the negative weight attributes of contactors.
Accordingly, there exists a need to provide electronic switching to reduce overall weight of an aircraft power system while also enhancing heat dissipation of devices used in the aircraft power system.